Title

Author

Access Type

Open Access Dissertation

Date of Award

January 2014

Degree Type

Dissertation

Degree Name

Ph.D.

Department

Psychology

First Advisor

Naftali Raz

Abstract

Fluid intelligence (Gf) and crystalized intelligence (Gc) are two factors of the general intelligence. They have distinct age-related trajectories of change. Jung and Haier proposed Parieto-Frontal Integration Theory (P-FIT, 2007) to account for the inter-person variance in reasoning intelligence. Some brain regions such as prefrontal, parietal, temporal and anterior cingulate cortices were included in the P-FIT model and were hypothesized to be involved in fluid reasoning task. Therefore, in the current study, we examined latent growth curves (LGC) of longitudinal change in Gf, Gc, prefrontal cortex, parietal cortex, anterior cingulate, temporal cortex and primary visual cortex. Forty-six healthy middle-aged and older adults were involved in baseline assessment. In addition, there were 3 follow-ups, and each of the 46 participants returned back for at least one follow-up. We observed longitudinal decline in Gf, which accelerated with advanced age. We proposed that the acceleration of Gf decline could be explained by age-related slowing. Intra-person longitudinal shrinkage was observed in the cortical thickness and volume of prefrontal, parietal, anterior cingulate and temporal cortices, but not in primary visual cortex. Furthermore, longitudinal shrinkage of surface area was observed in all the examined regions, including prefrontal, parietal, anterior cingulate, temporal and primary visual cortices, although the surface areas at baseline were not correlated with age. Nevertheless, no association was found between the parameters of cognitive change and parameters of cortical change.